Request for guidance on using SwiftPM dependencies

[rickpasetto]

I'm looking for some guidance. Reading the document, I ran across this:

If the module specifying the dependency is native, it will build and link the dependency as normal. Native Skip modules can use non-Skip packages, such as those tracked by the https://swift-everywhere.org/ site.

Does this imply that I can add a Pure Swift dependency that is "green" on https://swift-everywhere.org/ (for example, say, https://github.com/apple/swift-algorithms) to a Skip application for both iOS and Android? How would I go about doing that? Or am I mistaken? Thank you in advance for any guidance you can provide.

[marcprux]

Does this imply that I can add a Pure Swift dependency that is "green" on https://swift-everywhere.org/

Yes, although note that "green" on that chart just means that the package builds for Android – it doesn't run any tests, so YMMV.

(for example, say, https://github.com/apple/swift-algorithms)

That package does definitely work.

to a Skip application for both iOS and Android? How would I go about doing that? Or am I mistaken?

Take a look at the Skip Notes sample app. Its Package.swift uses the pure native swift-sqlcipher package to provide the database layer for the native model layer.

[rickpasetto]

Thank you so much for the quick reply!
This is great news, so it must mean I'm doing something wrong. I am trying to do this myself with the Travel Posters sample app. I just added swift-algorithms to its Package.swift:

...
    dependencies: [
        .package(url: "https://source.skip.tools/skip.git", from: "0.10.7"),
        .package(url: "https://source.skip.tools/skip-model.git", from: "0.0.0"),
        .package(url: "https://github.com/apple/swift-algorithms.git", from: "1.2.1")
    ],
    targets: [
        .target(
            name: "TravelPostersModel",
            dependencies: [
                .product(
                    name: "SkipModel",
                    package: "skip-model"
                ),
                .product(
                    name: "Algorithms",
                    package: "swift-algorithms"
                ),
            ],
            resources: [.process("Resources")],
            plugins: [.plugin(name: "skipstone", package: "skip")]
        ),
...

And then added a simple call to it in CityManager.swift:

import Algorithms
...
            self.allCities = try JSONDecoder().decode([City].self, from: Data(contentsOf: Self.localCitiesURL)).sorted { c1, c2 in
                c1.name < c2.name
            }
            .randomSample(count: 3)

...and I got it to compile and run just fine in iOS, but when I run skip export I get this error:

$ skip export
[✓] Check Swift Package (0.23s)
[✓] Getting SDK Path (0.01s)
[✓] Build project travel-posters-model (0.52s)
[✗] Assemble frameworks for TravelPostersModel (1.03s)
[✗] e: file:///Users/rick.pasetto/Documents/skipapp-travelposters/travel-posters-model/.build/plugins/outputs/travel-posters-model/TravelPostersModel/destination/skipstone/TravelPostersModel/src/main/kotlin/travel/posters/model/CityManager.kt:10:8 Unresolved reference 'algorithms'.
e: file:///Users/rick.pasetto/Documents/skipapp-travelposters/travel-posters-model/.build/plugins/outputs/travel-posters-model/TravelPostersModel/destination/skipstone/TravelPostersModel/src/main/kotlin/travel/posters/model/CityManager.kt:34:18 Unresolved reference 'randomSample'.
e: file:///Users/rick.pasetto/Documents/skipapp-travelposters/travel-posters-model/.build/plugins/outputs/travel-posters-model/TravelPostersModel/destination/skipstone/TravelPostersModel/src/main/kotlin/travel/posters/model/CityManager.kt:10:8 Unresolved reference 'algorithms'.
e: file:///Users/rick.pasetto/Documents/skipapp-travelposters/travel-posters-model/.build/plugins/outputs/travel-posters-model/TravelPostersModel/destination/skipstone/TravelPostersModel/src/main/kotlin/travel/posters/model/CityManager.kt:34:18 Unresolved reference 'randomSample'.

Is there more to it than just adding to Package.swift? Or am I doing something obviously wrong?

[marcprux]

I think the issue is that for native compiled Swift, you need to use the skipapp-travelposters-native app, rather than skipapp-travelposters.

[rickpasetto]

Apologies for the newbie questions...That's on me not understanding. Can you please help me understand the difference? Please feel free to point me at documentation! :)

[rickpasetto]

Ah, I just found this, sorry: https://skip.tools/docs/modes/#native

[rickpasetto]

Thanks for all of your help with this... the the skipapp-travelposters-native app seems to be the way to go, and that works.

But I've now run into my next roadblock in evaluating Skip: native (Android) compiled Swift seems to generate this error in Xcode for enums with associated values:

This release does not yet support bridging enums with additional state

I was able to get this error just by adding this as a test to CityManager.swift:

public enum CityType {
    case cool(Float)
    case warm(Int)
}

...I note that this doesn't have a problem in the transpiled project skipapp-travelposters. Is this really a limitation currently?

What is a bit strange is if I compile the project from the command line using skip android build, the resulting (exported) build does run and work in Android Studio. Puzzling.

Can you please help me understand this?

[marcprux]

Glad you are starting to get it to work!

Is this really a limitation currently?

The native toolchain supports all of Swift, including enums with associated types. However, SkipFuse also builds a bridge between the compiled Swift code and the UI-level Kotlin code, and this bridging does have some limitations, one of which is that it doesn't yet support enums with associated types.

The simples solution, if you don't need to access that type from Kotlin, would be to add the comment // SKIP @nobridge to the type, in which case Skip will not try to bridge it. Alternatively, if you make the type non-public, it will also not attempt to bridge the type.

[marcprux]

Update: actually, SkipFuse recently added support for enums with associated types. It may be that your packages are out of date – can you try running swift package update from the command-line, or File/Packages/Update the Latest Package Versions from Xcode, depending on which mechanism you are using to perform the build?

[rickpasetto]

Thank you! I will try that.